We discuss the anomalous magnetic moment of muon in the minimal supersymmetric model with and without right-handed neutrinos. In the same framework, the decay width of is also evaluated. Considering the measured val...We discuss the anomalous magnetic moment of muon in the minimal supersymmetric model with and without right-handed neutrinos. In the same framework, the decay width of is also evaluated. Considering the measured value of muon in the E821 experiment and other experimental constraints on the lepton-flavor-violation processes, we carry out numerical analysis on the concerned observables in the minimal supergravity scenario.展开更多
It is well known that excessively heavy supersymmetric particles(sparticles)are disfavored to explain the(g−2)_(μ) anomaly,but some people overlook that moderately light sparticles are also disfavored by the LHC prob...It is well known that excessively heavy supersymmetric particles(sparticles)are disfavored to explain the(g−2)_(μ) anomaly,but some people overlook that moderately light sparticles are also disfavored by the LHC probes of supersymmetry.We take the Next-to-Minimal Supersymmetric Standard Model as an example to emphasize the latter point.It is found that,if the theory is required to explain the anomaly at 2σlevel and meanwhile keep consistent with the LHC results,the following lower bounds may be set:tanβ&20,|M_(1)|&275 GeV,M_(2)&300 GeV,μ&460 GeV,m_(μL)&310 GeV,and m_(μR)&350 GeV,where M_(1)and M_(2)denote gaugino masses,μrepresents the Higgsino mass,and m_(μL)and m_(μR)are the mass of Smuons with L and R denot-ing their dominant chiral component.This observation has significant impacts on dark matter(DM)physics,e.g.,the popular Z-and Higgs-funnel regions have been excluded,and the Bino-dominated neutralino DM has to co-annihilate with the Wino-dominated electroweakinos(in most cases)and/or Smuons(in few cases)to obtain the correct density.It is also inferred that these conclusions keep valid for the Minimal Supersymmetric Standard Model since the underlying physics for the bounds are the same.展开更多
In this paper the anomalous magnetic dipole moment ofmuon in the littlest Higgs （LH） model is studied at one-loop level. We discuss the dependence of the contributions on the global symmetry breaking scale f, mizing...In this paper the anomalous magnetic dipole moment ofmuon in the littlest Higgs （LH） model is studied at one-loop level. We discuss the dependence of the contributions on the global symmetry breaking scale f, mizing angles c` and , and the Higgs triplet vacuum expectation value v＇ in the electroweak precision data preferring ranges. We find that the LH model can give a relatively small, but non-negligible extra weak contribution to the muon anomalous magnetic moment and can reduce the deviation of △aμ from 2.6σ for the SM to 2.5σ for the LH model.展开更多
BESⅢ合作组最近开始双光子物理研究,主要源于强子light-by-light散射对缪子反常磁矩的贡献有很大不确定性,电磁跃迁形状因子作为实验输入是改善计算精度的需要。在BESⅢ探测器上获得的质心能量3.77 Ge V到4.6Ge V的数据使得我们能够测...BESⅢ合作组最近开始双光子物理研究,主要源于强子light-by-light散射对缪子反常磁矩的贡献有很大不确定性,电磁跃迁形状因子作为实验输入是改善计算精度的需要。在BESⅢ探测器上获得的质心能量3.77 Ge V到4.6Ge V的数据使得我们能够测量轻赝标量介子的跃迁形状因子。在动量转移低于2(Ge V/c)2时单标记技术测量的结果达到前所未有的精确,该区域对于αμ的计算十分重要,并且也首次开始了π介子跃迁形状因子的双标记测量。这是π~0跃迁形状因子模型无关参数化研究的第一步。另外,多介子末态测量也在进行中.展开更多
The New Muon （g-2） Collaboration at Fermilab has proposed to measure the anomalous magnetic moment of the muon, αμ, a factor of four better than was done in E821 at the Brookhaven AGS, which obtained αμ = [1165...The New Muon （g-2） Collaboration at Fermilab has proposed to measure the anomalous magnetic moment of the muon, αμ, a factor of four better than was done in E821 at the Brookhaven AGS, which obtained αμ = [116592089（63）] × 10^-11 ±0.54 ppm. The last digit of a, is changed from the published value owing to a new value of the ratio of the muon-to-proton magnetic moment that has become available. At present there appears to be a difference between the Standard-Model value and the measured value, at the ≌ 3 standard deviation level when electron-positron annihilation data are used to determine the lowest-order hadronic piece of the Standard Model contribution. The improved experiment, along with further advances in the determination of the hadronic contribution, should clarify this difference. Because of its ability to constrain the interpretation of discoveries made at the LHC, the improved measurement will be of significant value, whatever discoveries may come from the LHC.展开更多
We review recent developments concerning the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. We first discuss why fully off-shell hadronic form factors should be used for ...We review recent developments concerning the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. We first discuss why fully off-shell hadronic form factors should be used for the evaluation of this contribution to the g- 2. We then reevaluate the numerically dominant pion-exchange contribution in the framework of large-No QCD, using an off-shell pion-photon-photon form factor which fulfills all QCD short-distance constraints, in particular, a new short-distance constraint on the off-shell form factor at the external vertex in g- 2, which relates the form factor to the quark condensate magnetic susceptibility in QCD. Combined with available evaluations of the other contributions to hadronic light-by-light scattering this leads to the new result αμ^LbyL;had= （116±40） × 10^-11, with a conservative error estimate in view of the many still unsolved problems. Some potential ways for further improvements are briefly discussed as well. For the electron we obtain the new estimate αe^LbyL;had= （3.9± 1.3） × 10^-14.展开更多
We update our Standard Model predictions for g-2 of the muon and for the hadronic contributions （5） 2 to the running of the QED coupling, Δαbad^5）（MZ^2）. Particular emphasis is put on recent changes in the had...We update our Standard Model predictions for g-2 of the muon and for the hadronic contributions （5） 2 to the running of the QED coupling, Δαbad^5）（MZ^2）. Particular emphasis is put on recent changes in the hadronic contributions from new data in the 2π channel and from the energy region just below 2 GeV.展开更多
After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that might explain the present discrepancy with the experimental value. None of them seems likely. In partic...After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that might explain the present discrepancy with the experimental value. None of them seems likely. In particular, a hypothetical increase of the hadroproduction cross section in low-energy e^＋e^- collisions could bridge the muon g-2 discrepancy, but it is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 135 GeV which, in conjunction with the experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.展开更多
We consider a model with multi-charged particles,including vector-like fermions,and a charged scalar under a local U(1)_(μ−τ) symmetry.We search for an allowed parameter region explaining muon anomalous magnetic mom...We consider a model with multi-charged particles,including vector-like fermions,and a charged scalar under a local U(1)_(μ−τ) symmetry.We search for an allowed parameter region explaining muon anomalous magnetic moment(muon g−2)and b→sℓ^(+)ℓ^(−) anomalies,satisfying constraints from the lepton flavor violations,Z boson decays,meson anti-meson mixing,and collider experiments.Via numerical analysis,we explore the typical size of the muon g−2 and Wilson coefficients to explain the b→sℓ^(+)ℓ^(−) anomalies in our model when all other experimental constraints are satisfied.Subsequently,we discuss the collider physics of the multicharged vectorlike fermions,considering a number of benchmark points in the allowed parameter space.展开更多
Because both W-mass and muon g-2 can be affected by mass splittings among extra Higgs bosons(H,A,H^(±))in a two-Higgs-doublet model,we take a model with μ-τ lepton flavor violation interactions to examine the t...Because both W-mass and muon g-2 can be affected by mass splittings among extra Higgs bosons(H,A,H^(±))in a two-Higgs-doublet model,we take a model with μ-τ lepton flavor violation interactions to examine the two anomalies reported by CDFⅡ and FNAL.We obtain the following observations:(ⅰ)Combined with theoretical constraints,the CDF W-mass measurement disfavors H or A degenerating in mass with H^(±)but allows H and A to degenerate.The mass splitting between H^(±)and H/A must be larger than 10 GeV.m_(H) and m_(A) are favored to be smaller than 650 GeV for m_(H)<120 GeV and allowed to have larger values with increasing m_(H).(ⅱ)After imposing other relevant experimental constraints,there are parameter spaces that simultaneously satisfy(at the 2σ level)the CDF W-mass,FNAL muon g-2,and data on lepton universality in τ decays;however,the mass splittings among extra Higgs bosons are strictly constrained.展开更多
The latest measurements of the anomalous muon magnetic moment a_(μ)≡(g_(μ)-2)/2show a 4:2σdiscrepancy between the theoretical prediction of the Standard Model and the experimental observations.To account for such ...The latest measurements of the anomalous muon magnetic moment a_(μ)≡(g_(μ)-2)/2show a 4:2σdiscrepancy between the theoretical prediction of the Standard Model and the experimental observations.To account for such a discrepancy,we consider a possible extension of the type-(I+II)seesaw model for neutrino mass generation with a gauged L_(μ)-L_(r)symmetry.By explicitly constructing an economical model with only one extra scalar singlet,we demonstrate that the gauge symmetry U(1)L_(μ)-L_(r)and its spontaneous breaking are crucial not only for explaining the muon result but also for generating the neutrino masses and leptonic flavor mixing.Various phenomenological implications and experimental constraints on the model parameters are also discussed.展开更多
文摘We discuss the anomalous magnetic moment of muon in the minimal supersymmetric model with and without right-handed neutrinos. In the same framework, the decay width of is also evaluated. Considering the measured value of muon in the E821 experiment and other experimental constraints on the lepton-flavor-violation processes, we carry out numerical analysis on the concerned observables in the minimal supergravity scenario.
基金supported by the National Natural Science Foundation of China(Grant No.12075076)。
文摘It is well known that excessively heavy supersymmetric particles(sparticles)are disfavored to explain the(g−2)_(μ) anomaly,but some people overlook that moderately light sparticles are also disfavored by the LHC probes of supersymmetry.We take the Next-to-Minimal Supersymmetric Standard Model as an example to emphasize the latter point.It is found that,if the theory is required to explain the anomaly at 2σlevel and meanwhile keep consistent with the LHC results,the following lower bounds may be set:tanβ&20,|M_(1)|&275 GeV,M_(2)&300 GeV,μ&460 GeV,m_(μL)&310 GeV,and m_(μR)&350 GeV,where M_(1)and M_(2)denote gaugino masses,μrepresents the Higgsino mass,and m_(μL)and m_(μR)are the mass of Smuons with L and R denot-ing their dominant chiral component.This observation has significant impacts on dark matter(DM)physics,e.g.,the popular Z-and Higgs-funnel regions have been excluded,and the Bino-dominated neutralino DM has to co-annihilate with the Wino-dominated electroweakinos(in most cases)and/or Smuons(in few cases)to obtain the correct density.It is also inferred that these conclusions keep valid for the Minimal Supersymmetric Standard Model since the underlying physics for the bounds are the same.
基金The project supported in part by National Natural Science Foundation of China and Special Fund sponsored by the Chinese Academy of Sciences
文摘In this paper the anomalous magnetic dipole moment ofmuon in the littlest Higgs （LH） model is studied at one-loop level. We discuss the dependence of the contributions on the global symmetry breaking scale f, mizing angles c` and , and the Higgs triplet vacuum expectation value v＇ in the electroweak precision data preferring ranges. We find that the LH model can give a relatively small, but non-negligible extra weak contribution to the muon anomalous magnetic moment and can reduce the deviation of △aμ from 2.6σ for the SM to 2.5σ for the LH model.
基金Supported by the German Research Foundation DFG under Contract(CRC-1044)
文摘BESⅢ合作组最近开始双光子物理研究,主要源于强子light-by-light散射对缪子反常磁矩的贡献有很大不确定性,电磁跃迁形状因子作为实验输入是改善计算精度的需要。在BESⅢ探测器上获得的质心能量3.77 Ge V到4.6Ge V的数据使得我们能够测量轻赝标量介子的跃迁形状因子。在动量转移低于2(Ge V/c)2时单标记技术测量的结果达到前所未有的精确,该区域对于αμ的计算十分重要,并且也首次开始了π介子跃迁形状因子的双标记测量。这是π~0跃迁形状因子模型无关参数化研究的第一步。另外,多介子末态测量也在进行中.
基金Supported by U.S. National Science Foundation and U.S. Department of Energy
文摘The New Muon （g-2） Collaboration at Fermilab has proposed to measure the anomalous magnetic moment of the muon, αμ, a factor of four better than was done in E821 at the Brookhaven AGS, which obtained αμ = [116592089（63）] × 10^-11 ±0.54 ppm. The last digit of a, is changed from the published value owing to a new value of the ratio of the muon-to-proton magnetic moment that has become available. At present there appears to be a difference between the Standard-Model value and the measured value, at the ≌ 3 standard deviation level when electron-positron annihilation data are used to determine the lowest-order hadronic piece of the Standard Model contribution. The improved experiment, along with further advances in the determination of the hadronic contribution, should clarify this difference. Because of its ability to constrain the interpretation of discoveries made at the LHC, the improved measurement will be of significant value, whatever discoveries may come from the LHC.
基金Supported by Funding from the Department of Atomic Energy,Government of India,for the Regional Centre for Accelerator-based Particle Physics (RECAPP),Harish-Chandra Research Institute
文摘We review recent developments concerning the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. We first discuss why fully off-shell hadronic form factors should be used for the evaluation of this contribution to the g- 2. We then reevaluate the numerically dominant pion-exchange contribution in the framework of large-No QCD, using an off-shell pion-photon-photon form factor which fulfills all QCD short-distance constraints, in particular, a new short-distance constraint on the off-shell form factor at the external vertex in g- 2, which relates the form factor to the quark condensate magnetic susceptibility in QCD. Combined with available evaluations of the other contributions to hadronic light-by-light scattering this leads to the new result αμ^LbyL;had= （116±40） × 10^-11, with a conservative error estimate in view of the many still unsolved problems. Some potential ways for further improvements are briefly discussed as well. For the electron we obtain the new estimate αe^LbyL;had= （3.9± 1.3） × 10^-14.
文摘We update our Standard Model predictions for g-2 of the muon and for the hadronic contributions （5） 2 to the running of the QED coupling, Δαbad^5）（MZ^2）. Particular emphasis is put on recent changes in the hadronic contributions from new data in the 2π channel and from the energy region just below 2 GeV.
基金Supported by U.S.DOE grant DE-AC02-76CH00016E.C.contract MRTN-CT 2006-035505U.S. NSF grant PHY-0758032
文摘After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that might explain the present discrepancy with the experimental value. None of them seems likely. In particular, a hypothetical increase of the hadroproduction cross section in low-energy e^＋e^- collisions could bridge the muon g-2 discrepancy, but it is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 135 GeV which, in conjunction with the experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.
基金supported by an appointment to the JRG Program at the APCTP through the Science and Technology Promotion Fund and Lottery Fund of the Korean Government。
文摘We consider a model with multi-charged particles,including vector-like fermions,and a charged scalar under a local U(1)_(μ−τ) symmetry.We search for an allowed parameter region explaining muon anomalous magnetic moment(muon g−2)and b→sℓ^(+)ℓ^(−) anomalies,satisfying constraints from the lepton flavor violations,Z boson decays,meson anti-meson mixing,and collider experiments.Via numerical analysis,we explore the typical size of the muon g−2 and Wilson coefficients to explain the b→sℓ^(+)ℓ^(−) anomalies in our model when all other experimental constraints are satisfied.Subsequently,we discuss the collider physics of the multicharged vectorlike fermions,considering a number of benchmark points in the allowed parameter space.
基金Supported by the National Natural Science Foundation of China(11975013,12105248,11821505,12075300,12075213)Peng-Huan-Wu Theoretical Physics Innovation Center(12047503)+1 种基金the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP)the Key Research Program of the Chinese Academy of Sciences(XDPB15)。
文摘Because both W-mass and muon g-2 can be affected by mass splittings among extra Higgs bosons(H,A,H^(±))in a two-Higgs-doublet model,we take a model with μ-τ lepton flavor violation interactions to examine the two anomalies reported by CDFⅡ and FNAL.We obtain the following observations:(ⅰ)Combined with theoretical constraints,the CDF W-mass measurement disfavors H or A degenerating in mass with H^(±)but allows H and A to degenerate.The mass splitting between H^(±)and H/A must be larger than 10 GeV.m_(H) and m_(A) are favored to be smaller than 650 GeV for m_(H)<120 GeV and allowed to have larger values with increasing m_(H).(ⅱ)After imposing other relevant experimental constraints,there are parameter spaces that simultaneously satisfy(at the 2σ level)the CDF W-mass,FNAL muon g-2,and data on lepton universality in τ decays;however,the mass splittings among extra Higgs bosons are strictly constrained.
基金Supported in part by the National Natural Science Foundation of China(11775232,11835013)the CAS Center for Excellence in Particle Physics。
文摘The latest measurements of the anomalous muon magnetic moment a_(μ)≡(g_(μ)-2)/2show a 4:2σdiscrepancy between the theoretical prediction of the Standard Model and the experimental observations.To account for such a discrepancy,we consider a possible extension of the type-(I+II)seesaw model for neutrino mass generation with a gauged L_(μ)-L_(r)symmetry.By explicitly constructing an economical model with only one extra scalar singlet,we demonstrate that the gauge symmetry U(1)L_(μ)-L_(r)and its spontaneous breaking are crucial not only for explaining the muon result but also for generating the neutrino masses and leptonic flavor mixing.Various phenomenological implications and experimental constraints on the model parameters are also discussed.
